1. Field of the Invention
The present invention relates to an electric motor.
2. Description of Related Art
In general, in a case of an electric motor, which includes a rotatable shaft and an armature, a brush holder is fitted to an opening of a yoke housing of the motor to provide electric power for rotating the armature, and terminals are installed in the brush holder. One end of each terminal is connected to a corresponding brush, which is supported by the brush holder, and the other end of the terminal is connected to a terminal of an external connector, which is connected to an external power source. The electric power, which is received from the external power source, is supplied to the brushes to rotate the armature.
In the prior art structure, in order to reduce a size of the motor in the axial direction to implement a low profile motor, the terminals protrude from the lateral side of the brush holder to connect with the terminals of the external connector (see, for example, Japanese Unexamined Patent Publication No. 2003-111349).
The motor recited in Japanese Unexamined Patent Publication No. 2003-111349 includes an armature, a yoke housing and a brush holder. A rotatable shaft and a commutator are provided in the armature. The yoke housing is cup-shaped and rotatably receives the armature. The brush holder closes an opening end of the yoke housing and holds brushes, which slidably engage the commutator.
As shown in FIG. 6A, the brush holder 101 includes a holder main body 102, a connector portion 103 and an interconnecting portion 104. The holder main body 102 is fitted in the yoke housing and holds the brushes. The connector portion 103 is disposed radially outward of the holder main body 102 and is connected with terminals of an external connector 110. The interconnecting portion 104 connects between the holder main body 102 and the connector portion 103. The terminals 105 are inserted such that the terminals 105 extend over the holder main body 102, the connector portion 103 and the interconnecting portion 104. One end (a brush contact) of each terminal 105 is connected to the corresponding brush, and the other end (a terminal connection 105a) of the terminal 105 is disposed in an opening 103a of the connector portion 103.
The external connector 110 is inserted in the opening 103a of the connector portion 103, so that the terminals of the external connector 110 are connected with the other ends of the terminals 105 (the terminal connections 105a). As described above, the terminals 105 protrude radially outward from the brush holder 101, so that it is not required to axially expand the brush holder 101. Thereby, it is possible to reduce a size of the brush holder 101 in the axial direction.
As shown in FIG. 6B, fitting grooves 101a extend along the holder main body 102, the connector portion 103 and the interconnecting portion 104. The terminals 105 are fitted into the fitting grooves 101a, respectively, and thereby installed in the brush holder 101.
In the motor having the above structure, an installation direction (a direction of an arrow X in FIG. 6B) of the terminals 105 for installing the terminals 105 into the brush holder 101 is the same as a connecting direction of the terminals 105 for connecting the terminals 105 to the terminals of the external connector 110. Furthermore, a power supply line extends from the terminal 105 to the brush. Thus, when the external connector 110 is pulled away from the terminal connections 105a, the terminal connection 105a side of the terminals 105 are pulled in a pulling direction of the external connector 110 (a direction opposite from the installation direction), and thereby the terminals 105 are sometimes unintentionally removed from the fitting grooves 101a of the brush holder 101.
According to another technique, a portion of a terminal is cut and is bent to form a resilient engaging piece in the terminal, and a corresponding engaging hole is formed in a connector housing and is engaged with the resilient engaging piece to limit unintentional removal of the terminal from the connector housing (see, for example, Japanese Unexamined Patent Publication No. 11-3739). With this structure, even when a force acts on the terminal in the pulling direction, the resilient engaging portion of the terminal is effectively engaged with a wall of the engaging hole to resist against the pulling of the terminal, so that the unintentional removal of the terminal from the connector housing is limited, and thereby the terminal can be reliably held.
However, when the removal limiting structure of Japanese Unexamined Patent Publication No. 11-3739 is applied to the motor of Japanese Unexamined Patent Publication No. 2003-111349, in which the terminals radially outwardly protrude, the following disadvantage may be encountered.
That is, in the motor of Japanese Unexamined Patent Publication No. 2003-111349, an extension of the terminal, which connects between the terminal connection and the brush contact of the terminal, is fitted into the fitting hole of the housing. Thus, when the terminal connection of the terminal is pulled in the pulling direction, the terminal is tilted about a portion (fulcrum) of the extension. When the terminal is kept tilted further, the terminal is finally removed from the fitting groove of the brush holder.
Therefore, even in the case where the removal limiting structure of Japanese Unexamined Patent Publication No. 11-3739 is applied to the motor of Japanese Unexamined Patent Publication No. 2003-111349, when the external connector is pulled away from the terminals, the terminals are tilted, so that the engagement between the resilient engaging portion of each terminal and the housing may possibly be released by the tilting of the terminal, resulting in the removal of the terminal from the housing.
Furthermore, a width of the terminal of Japanese Unexamined Patent Publication No. 2003-111349 is relatively small. Therefore, it is difficult to form the resilient engaging portion by the cutting and pulling of the corresponding portion in the plate thickness direction in the terminal. Furthermore, the engaging hole needs to be formed in the housing (the brush holder in Japanese Unexamined Patent Publication No. 2003-111349), so that it is difficult to form the housing.